Patterns ofCryptosporidiumOocyst Shedding by Eastern Grey Kangaroos Inhabiting an Australian Watershed

Abstract

The occurrence of Cryptosporidium oocysts in feces from a population of wild eastern grey kangaroos inhabiting a protected watershed in Sydney, Australia, was investigated. Over a 2-year period, Cryptosporidium oocysts were detected in 239 of the 3,557 (6.7%) eastern grey kangaroo fecal samples tested by using a combined immunomagnetic separation and flow cytometric technique. The prevalence of Cryptosporidium in this host population was estimated to range from 0.32% to 28.5%, with peaks occurring during the autumn months. Oocyst shedding intensity ranged from below 20 oocysts/g feces to 2.0 ؋ 10 6 oocysts/g feces, and shedding did not appear to be associated with diarrhea. Although morphologically similar to the human-infective Cryptosporidium hominis and the Cryptosporidium parvum "bovine" genotype oocysts, the oocysts isolated from kangaroo feces were identified as the Cryptosporidium "marsupial" genotype I or "marsupial" genotype II. Kangaroos are the predominant large mammal inhabiting Australian watersheds and are potentially a significant source of Cryptosporidium contamination of drinking water reservoirs. However, this host population was predominantly shedding the marsupial-derived genotypes, which to date have been identified only in marsupial host species.

A New Species of Cryptosporidium (Apicomplexa: Cryptosporidiidae) from Eastern Grey Kangaroos (Macropus giganteus)

“…In contrast, C. macropodum was identified in captive western grey and red kangaroos during summer (Thompson, 2007). The pathogenicity of C. macropodum to marsupials is relatively unknown, but data indicate that this species is adapted to marsupials as oocyst shedding in eastern grey kangaroos ranged from 10 to 2.0 ϫ 10 6 oocysts per gram and that samples with high oocyst loads were not associated with diarrhea (Power et al, 2005).…”

“…In another recent study, C. macropodum was identified in 6 of 10 fecal samples from western grey kangaroos and 3 of 30 samples from red kangaroos (Thompson, 2007). The eastern grey kangaroo study demonstrated cyclic shedding patterns, with C. macropodum dominating during the cooler months and C. fayeri dominating during periods when the population contained high numbers of juveniles (Power et al, 2005). In contrast, C. macropodum was identified in captive western grey and red kangaroos during summer (Thompson, 2007).…”

“…Epidemiology studies on marsupials have indicated that C. macropodum is host adapted to marsupial species as demonstrated by absence of clinical signs in marsupial hosts despite excretion of high oocyst numbers (Power et al, 2005;Thompson, 2007). There are no reports of experimental infections in any host species for C. macropodum.…”

“…Limited data are available for the prevalence of C. macropodum in marsupials, but a study of eastern grey kangaroos inhabiting an Australian watershed detected oocysts in 239 of 3,557 (6.7%) fecal samples screened and demonstrated that C. macropodum was present in 39% of the samples that were genotyped, with C. fayeri being present in the remaining 61% of samples (Power et al, 2005). In another recent study, C. macropodum was identified in 6 of 10 fecal samples from western grey kangaroos and 3 of 30 samples from red kangaroos (Thompson, 2007).…”

“…Oocysts were purified from eastern grey kangaroo feces by using immunomagnetic separation as described previously (Power et al, 2005). Measurements of length and width were obtained from oocysts (n ϭ 50) purified from an individual sample that represents the type specimen.…”